Commentary

A high-level line-only preamplifier that inherits from the C-280V and completely replaces the original C-270.

The line amplifier section employs a balanced transmission circuit similar to the C-280V. Balanced transmission is a method of simultaneously transmitting positive and negative symmetrical signals whose phases are inverted with each other. It has an excellent ability to eliminate common-mode noise components.
The C-280V line amplifier basically consists of three differential amplifiers for balanced transmission. amp1 is used as an input, and amp2 and amp3 are used as outputs. The signals from both + - inputs of amp1 are amplified and then input to the following amp2 and amp3. These two amplifiers feed back their outputs to the other side. They transmit a + - symmetric signal with low impedance.
For unbalanced connections, simply connect the terminals on either side of the input / output side to the ground line.

The C-270V is equipped with a line amplifier for unbalanced output and a line amplifier for balanced output separately.
The line amplifier for unbalanced output has an all-FET constant-current load cascode bootstrap source follower at the input, which is amplified by a symmetrical balanced differential push-pull emitter-grounded circuit with a high in-phase rejection ratio, and a symmetrical cascode push-pull + emitter-follower circuit at the output.
In the line amplifier for balanced output, the balanced output circuit is added to the dedicated input circuit like the unbalanced output amplifier. This output circuit is similar to the C-280V, and the balanced output is composed by bridge feedback which applies feedback to the opposite amplifier of inverted amplifier and non-inverted amplifier respectively. Both inverted and non-inverted outputs are completely separated from the ground.
All of these unit amplifiers are DC-servo for both input and output, and no capacitor is inserted to cut DC.

The power supply section has a completely monophonic configuration with independent transformers and filter capacitors on the left and right sides. In addition, all unit amplifiers are equipped with a broadband low-impedance power supply to prevent mutual interference between amplifiers.

For the volume that has a large impact on sound quality, a 4-linked volume regulator with CP (conductive plastic) elements is used.
The CP element used in the studio is used for the resistor. After the resistor element is printed, it is molded under high temperature pressure, and the surface of the element is finished into a mirror surface to achieve low contact resistance and low distortion.
The brush that contacts the resistor is a gold-plated multi-contact type. It is integrated with the external terminal to eliminate the metal contact surface and reduce the strain caused by contact of different metals.
In addition, the rotation method has a structure in which the resistor rotates instead of the method in which the brush rotates. This greatly reduces internal contact points, eliminates the need for contact grease, and improves durability.
The casing of the sound quality adjuster is an 8 mm diameter thick brass shaft supported by an aluminum cutting bearing, and four elements are each housed in a high-precision aluminum cutting case to provide a complete shield to improve sound quality.
The variable method is a continuously variable type with a tracking error of less than 0.5 dB measured at a position of -60dB.

A logic relay control circuit is used to switch the input signal.
In this system, highly reliable relays are installed in each local area, and the timing of switching is controlled by a logic circuit, thus preventing wiring and sound quality degradation.
The relay uses a completely sealed structure filled with nitrogen gas, which was developed especially for audio and communication equipment. The gold and silver-palladium alloy cross-bar twin system for the contacts that affect sound quality realizes low contact resistance and high durability.

The C-270V consists of a line amplifier for unbalanced output and a line amplifier for balanced output separated into two units. Each unit amplifier is paired with a printed circuit board and a local area power supply, which is less susceptible to interference, and housed in a thick aluminum housing.
They are mounted on a large motherboard for electrical stability and serviceability, and are mounted on an 8-mm aluminum chassis to prevent electrical and mechanical interference.

Equipped with a dedicated direct-coupled headphone amplifier.

The input / output jack is a characteristic jack with rhodium plating for excellent durability.

Equipped with a 3-step attenuator.

Equipped with left and right independent attenuator level control for perfect channel balance and control of orientation in any listening position. It can be adjusted in 0.5 db steps from 0 to -6dB and in 1 db intervals from -14dB.
The resistance element uses a mirror finished low-distortion type.

It is equipped with a phase switch which inverts the phase of the whole device.
In the switching method, only + - of the balance amplifier input is replaced, and there is no additional circuit like a phase inverter, so there is no sound quality degradation.

It is equipped with a compensator switch to compensate for the lack of volume at low volume, and the characteristics are automatically corrected according to the position of the volume adjuster.

A monitor switch is installed so that two tape recorders can be connected for recording, playback and monitoring.
A special balance / unbalance conversion circuit is provided so that the tape relation can be used in the same way as in the case of unbalance. It is also possible to copy between tape recorders.
In addition, the tuner output is output to the tape recorder output terminal even when the C-270V power is turned off.

Natural Persimmon finished boards are installed on both sides.

Model Rating

Type	Stereo Preamplifier
Frequency Response	balanced input (CD, Line) : 1.0 Hz to 300 kHz + 0 -3.0 dB 20 Hz ~ 20 kHz + 0 -0.2 dB CD, Tuner, Line, Tape Play : 1.0 Hz to 300 kHz + 0 -3.0 dB 20 Hz ~ 20 kHz + 0 -0.2 dB
Total Harmonic Distortion Factor	0.005% (at all input terminals)
Input sensitivity / impedance (at rated output / 0.5 V output)	Balanced : 252mV/63mV/40k Ω Unbalanced : 252mV/63mV/20k Ω
Rated Output / Impedance	Balanced output : 2.0V/50 ohm Unbalanced output : 2.0V/1 ohm Tape rec : 252mV/100 Ω
Headphone jack	Applicable Impedance : 4 Ω ~ 600 Ω
S/N / Input conversion noise	Input Short IFF-A Correction Input Terminal Rated Input S/N Input Conversion Noise EIA S/N Balanced: 110dB -122dBV 94dB Unbalanced: 110dB -122dBV 94dB
Maximum power level (0.005% distortion rate, 20 Hz to 20 kHz)	Balanced output:7.0V Unbalanced output:7.0V Tape rec:7.0V
Minimum Load Impedance	Balanced output : 600 ohms Unbalanced output : 1k Ω Tape rec : 10k Ω
Gain	Balanced input → Balanced output : 18 dB Balanced input → Unbalanced output : 18 dB Balanced input → rec output : 0 dB Unbalanced input → Balanced output : 18 dB Unbalanced input → Unbalanced output : 18 dB Unbalanced input → rec output : 0 dB
Loudness Compensator (Volume -30dB)	1:+3dB(100Hz) 2 : + 8 dB at 100 Hz, + 6 dB at 20 kHz
Attenuator	-20dB, -30dB, ∞
Semiconductors used	Transistors : 74 FET : 36 IC : 25 pcs Diode : 97
Power Supply Voltage	100 VAC / 117 V / 220 V / 240 V, 50Hz/60Hz
Power Consumption	18W
External Dimensions	468 mm wide x 149 mm high x 403 mm deep
Weight	22.0kg